Question: What are gene drives?
It is now possible to engineer inheritance so a particular gene variant is preferentially passed to the next generation. Over time the variant would spread through the population. This is called a gene drive.
To put this into context, consider some examples of how gene drives could be used. Firstly, they might be used to prevent mosquito populations from carrying diseases such as malaria. Secondly, they might protect biodiversity by eliminating feral rodents from islands where they devour the eggs of endangered birds. Or they might limit the burden of weeds and insect-pests on agricultural production.
Gene drives occur naturally, although rarely, and have fascinated geneticists for decades. Essentially they occur when gene variants are inherited more frequently than expected by the laws established by Gregor Mendel in the 1800s.
Consider a gene passed from a female Anopheles mosquito to her offspring. Normally about half of her 50-200 eggs will be expected to contain the gene variant she inherited from her father, and the other half will have the gene variant she received from her mother. However, if there is a mechanism that ensures that only one variant is found in the eggs, and therefore passed to the next generation, then that variant is likely to increase in frequency in the population over multiple generations.
Recent advances in gene-editing technologies mean that it is now possible to create synthetic gene drives that contain a desired gene (eg, a gene that interferes with the replication of malaria-causing parasites within mosquitos). The profound way in which gene drives differ from the genetically modified organisms we have in the environment today is that there is an explicit intention for the introduced gene to spread in a free-living, free-breeding population.
Gene drives only work in sexually reproducing organisms and would only be effective in organisms with short generation times. Most imagined applications involve pest organisms although people have speculated about applying the technology to crops, livestock or even native animals.
Recently the Australian Academy of Science released a discussion paper considering the implications of synthetic gene drives, including ecological hazards, ethical concerns, and other potential impacts. The paper, titled Synthetic gene drives in Australia, is available on the academy's website.
Response by: Dr Charles Robin, school of biosciences, the University of Melbourne
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